Coaxial inductive device and enclosing case therefor



June 2, 1959 w. L. R. HENDERSON 2,889,523 1 COAXIAL INDUCTIVE DEVICE AND ENCLOSING CASE THEREFOR Filed Sept. 12, 1955 fm/entorz' WsyzzeLf/andemon, by Wdv his fitter/7e3- United States invention relates to inductive devices such as transformers and reactors, and more particularly to coaxial inductive devices and to enclosing cases therefor.

Inductive devices are commonly used to modify an alternating current quantity; transformers being utilized to increase or decrease an alternating current voltage while reactors are utilized to limit alternating current. A special form of inductive device commonly referred to as a high reactance transformer, functions both as a voltage modifying and current limiting device, and is commonly used for starting and operating arc discharge devices such as fluorescent lamps. Inductive devices generally comprise a core portion formed ofmagnetic mate- 'rial with one or more electrical coils positioned thereon and another core portion also formed of magnetic material for providing a return path for the magnetic flux produced by the coils. In the past, the cores of inductive devices have generally been formed of a stack of relalively thin flat laminations of magnetic material punched or otherwise formed from a larger sheet of such material. This construction, however, "frequently resulted in a substantial waste of expensive magnetic material and further resulted in a configuration which when housed in an enclosing case was unduly large and thus wasteful of space.

These factors have led to the development of the so called coaxial construction of inductive device. The coaxial inductive device conventionally 'cdinprises a cylindrical center winding leg core member on which the coil or coils are arranged with annular core portions formed on the ends thereof and with an "outer cylindrical yoke core member concentrically surrounding the center member and coils. Such a device is more fully described in c'o 'pending application, Serial Number 524,003 filed July ".25, 1955, of Jerry L. Stratton, assigned to the assignee of the present application. V

While the coaxial type of device provides a much more efficient utilization 'of magnetic material and a smaller overall size, it is necessary to provide means for holding the components of the device in assembled relation and for housing and mounting the device. It is further desirable to provide a coaxial type device which including its enclosing case is simple and readily assembled.

It is 'therefo'rea general object of this invention to provide an improved coaxial type inductive'device.

Another object *of this invention is to provide an improved coaxial type inductive device including housing and mounting means incorporating the advantages enumerated above.

A 'A funther object of this invention is 'to provide an enclosing case for a coaxial type inductive device.

Further objects and advantages of this invention will become apparent and the invention will be better understood by reference to the following description and the accompanying drawing, and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

atent Patented June 2, 1959 I joins the annular portions on the exterior of'the coil.

The yoke member has a semi-circular crosssection thereby 'exposing a portion of 'coil, and a cover member is provided also having a semi-circular cross-section surrounding the yoke member. The word semi-circular is used herein in a hyphenated form to mean less than a complete circle and is not intended to mean a precise half circle. Preferably, in accord with the invention, the cross sections of the yoke member and cover member are considerably more than a half circle. A base member completes the assembly by engaging the cover member thereby enclosing the exposed portion of the coil.

in the drawing,

Fig. 1 is a View in perspective showing the improved coaxial inductive device of this invention; incorporating the improved housing and mounting means;

Fig. 2 is a partially-exploded view illustrating the construction of Fig. hand Fig. 3 is a cross-section view taken along the line 3-3 of Fig. 1.

Referring now to the drawing", there is shown a coaxial inductive device, generally identified as 1, the specific embodiment shown here being a high reactance ballast transformer for operating fluorescent lamps; The coaxial inductive device 1 comprises a substantial cylindrical center winding leg member 2, shown here as being formed of a bundle of iron wires. Annular portions 3 and 4 respectively formed of "a plurality of relatively thin, radially split, washer-shaped laminations 5 of magnetic material a are arranged on the center leg 2 respectively adjacent the ends thereof and suitable-coils 6'and 7 are/positioned on center leg 2 intermediate the annular portions 3 and 4. While a high reactance transformer construction is shown, it will be readily understood that the particular arrangement of coils shown is not; a part of this invention and that this invention is equally applicable to high or low reactance transformers or to reactors. A yoke portion 8 is provided having a semi-circular cross-section and engaging the peripheral surfaces of the annular portions 3 and 4. Yoke member'Sis formed of a plurality of fiat, straight, axially extending, radially arranged laminations 9 of magnetic material. It will be observed that the yoke member 8 only partiall-ysurrounds annular portions 3 and 4 and coils 6 and 7, thus exposing a portion of each of the coils 6 and 7. p

In order to hold the laminations 9 comprising the yoire member 8 in assembled relation and to enclose the device 1, a [cover member 10 is provided, preferably formed of relatively thin metal, also having a semi-circular cross-section. Cover member 10 surrounds yoke member 8 and has inwardly turned tportions '11 respectively formed on its circumferential ends. Inwardly turned portions 11 respectively engage the circumferential ends of yoke member 8 thus holding the laminations 9 in assembled relation. Cover member 10 also has inwardly turned annular ilan-ges 12 respectively formed 'atits axial ends which respectively engage the axial ends of yoke member 8. Also formedon the circumferential ends of cover member to are outwardly extending portions 13 which are engaged by inwardly inclined legs 14 of channel-shaped base member 15. It will new be readily seen that base member 15 may be sue over outwardly turned portions 13 of cover member 10 thereby enclosing the exposed portions of coils 6 and 7.

Reference to Fig. 3 will clearly show that the web portion 16 of base member 15 is spaced from the exposed portions of annular portions 3 and 4 and coils 6 and 7, as at 17. Electrical leads 18 and 19 are provided for making the necessary electrical connections to coils 6 and 7. Leads 18 and 19 extend through spaces 17 between web portion 16 of base member 15 and annular portions 3 and 4 and are electrically connected to the exposed portions of coils 6 and 7, as at 20. In order to hold the completed device in assembled relation, portions 21 and 22 of base member 15 which extend be yond the axial ends of center member 2 and yoke member 8 have their legs 14 crimped downwardly, as at 22. Extension portion 21 and 22 of base member 15 may be provided with suitable slots 23 for mounting the device.

It will now be seen that this invention provides a simple and readily assembled construction for coaxial type inductive devices wherein the laminations comprising the yoke member are held in assembled relation, the yoke member, center member and coils are held in assembled relation, the external leads are conveniently brought out, and a simple housing and mounting arrangement is provided.

While I have shown and described a specific embodiment of this invention, further modifications and improvements will occur to those skilled in the art. It is to be understood therefore that this invention is not limited to the particular form shown, and I intend in the appended claims to cover all modifications Within the spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A coaxial inductive device comprising a substantially cylindrical center winding leg member formed of magnetic material, annular magnetic portions respectively adjacent the ends of said center member, a coil positioned on said center member intermediate said annular portions, a yoke member extending axially over the exterior of said coil and said annular magnetic portions, said yoke member being formed of a plurality of relatively thin axially extending radially arranged laminations of magnetic material, said yoke member having a cross-section of less than a complete circle and more than a half circle thereby exposing a portion of the peripheries of said coil and said annular portions, a cover member surrounding and holding together the laminations of said yoke member, said cover member having a cross-section of less than a complete circle and more than a half circle, and a base member engaging and holding the circumferential ends of said cover member and spaced from said exposed portions of said coil and said annular portions.

2. A coaxial inductive device comprising a substantially cylindrical center winding leg member formed of magnetic material, annular magnetic portions respectively adjacent the ends of said center member, a coil positioned on said center member intermediate said annular portions, a yoke member extending axially over the ex-' terior of said coil and said annular magnetic portions, said yoke member being formed of a plurality of relatively thin axially extending radially arranged laminations of magnetic material, said yoke member having a cross-section of less than a complete circle and more than a half circle thereby exposing a portion of the peripheries of said coil and said annular portions, a cover member surrounding the peripheral surface of said yoke member and having portions respectively engaging the circumferential ends of said yoke member thereby holding said laminations in assembled relation, said cover member having a cross-section of less than a complete circle and more than a half circle, and a base member engaging and holding the circumferential ends of said cover member and spaced from said exposed portions of said coil and said annular portions.

3. A coaxial inductive device comprising a substantially cylindrical center winding leg member formed of magnetic material, annular magnetic portions respectively adjacent the ends of said center member, a coil positioned on said center member intermediate said annular portions, a yoke member extending axially over the exterior of said coil and said annular magnetic portions, said yoke member being formed of a plurality of relatively thin axially extending radially arranged laminations of magnetic material, said yoke member having a crosssection of less than a complete circle and more than a half circle thereby exposing a portion of the peripheries of said coil and said annular portions, a cover member having a cross-section of less than a complete circle and more than a half circle contiguously surrounding the peripheral surface of said yoke member and having inwardly turned portions formed on its circumferential ends respectively engaging the circumferential ends of said yoke member thereby holding said laminations in assembled relation, said circumferential ends of said cover member having outwardly turned portions formed thereon, and a base member having a channel-shaped crosssection with the legs thereof inwardly inclined and engaging said cover member outwardly turned portions, said base member being spaced from said exposed portions of said coil and said annular portions.

4. A coaxial inductive device comprising a substantially cylindrical center winding leg member formed of magnetic material, annular magnetic portions respectively adjacent the ends of said center member, a coil positioned on said center member intermediate said annular portions, a yoke member extending over the exterior of said coil and said annular magnetic portions, said yoke member being formed of a plurality of relatively thin axially extending radially arranged laminations of magnetic material, said yoke member having a cross-section of less than a complete circle and more than a half circle thereby exposing a portion of the peripheries of said coil and said annular portions, a cover member having a cross-section of less than a complete circle and more than a half circle surrounding the peripheral surface of said yoke member and having inwardly turned portions formed on its circumferential ends respectively engaging the circumferential ends of said yoke member thereby holding said laminations in assembled relation, said cover member having inwardly turned annular flanges formed at its axial ends respectively engaging the axial ends of said yoke member, said circumferential ends of said cover member having outwardly turned portions formed thereon, and a base member having a channel-shaped cross-section with the legs thereof inwardly inclined and engaging said covert member outwardly turned portions, said base member being spaced from said exposed portions of said coil and said annular portions, said base member having portions extending respectively beyond the axial ends of said yoke member, said base member extension portions having their legs crimped thereby to hold said device in assembled relation and having mounting means formed thereon.

5. A coaxial inductive device comprising a substantially cylindrical center winding leg member formed of magnetic material, annular magnetic portions respectively adjacent the ends of said center member, a coil positioned on said center member intermediate said annular portions, a yoke member extending over the exterior of said coil and said annular magnetic portions, said yoke member being formed of a plurality of relatively thin, fiat, straight, radially arranged laminations of magnetic material, said yoke member having a cross-section of less than a complete circle and more than a half circle thereby exposing a portion of the peripheries of said coil and said annular portions, a cover member having a cross-section of less than a complete circle and more than a half circle surrounding the peripheral surface of said yoke member and having inwardly turned portions formed on its circumferential ends respectively engaging the circumferential ends of said yoke member thereby holding said laminations in assembled relation, said cover member having inwardly turned annular flanges formed at its axial ends respectively engaging the axial ends of said yoke member, said circumferential ends of said cover member having outwardly turned portions formed thereon, and a base member having a channel-shaped cross-section with its legs inwardly inclined and engaging said cover member outwardly turned portions, said base member being spaced from said exposed portions of said coil and said annular portions.

6. A coaxial inductive device comprising a substantially cylindrical center winding leg member formed of magnetic material, annular portions formed of a plurality of relatively thin washer-shaped laminations of magnetic material assembled on said center member respectively adjacent the ends thereof, a coil positioned on said center member intermediate said annular portions, a yoke member engaging the peripheral surfaces of said annular portions and extending over the exterior of said coil, said yoke member being formed of a plurality of relatively thin, flat, straight, radially arranged laminations of magnetic material, said yoke member having a cross-section of less than a complete circle and more than a half circle thereby exposing a portion of the peripheries of said coil and said annular portions, a cover member having a crosssection of less than a complete circle and more than a half circle surrounding the peripheral surface of said yoke member and having inwardly turned portions formed on its circumferential ends respectively engaging the circumferential ends of said yoke member holding said laminations in assembled relation, said cover member having inwardly turned annular flanges formed at its axial ends respectively engaging the axial ends of said yoke member, said circumferential ends of said cover member having outwardly turned portions formed thereon, and a base member having a channel-shaped cross-section with the legs thereof inwardly inclined and engaging said cover member outwardly turned portions, said base member being spaced from said exposed portions of said coil and said annular portions.

7. A coaxial inductive device comprising a substantially cylindrical center winding leg member formed of magnetic material, annular magnetic portions respectively adjacent the ends of said center member, a coil positioned on said center member intermediate said annular portions, a yoke member magnetically joining said annular portions on the exterior of said coil, said yoke member being formed of a plurality of relatively thin axially extending radially arranged laminations of magnetic material, said yoke member having a cross-section of less than a complete cycle and more than a half circle thereby exposing a portion of said coil, a cover member having a crosssection of less than a complete circle and more than a half circle surrounding the peripheral surface of said yoke member, the circumferential ends of said cover member having outwardly turned portions formed thereon, and a base member having a channel-shaped cross-section with the legs thereof inwardly inclined and engaging said cover member outwardly turned portions thereby enclosing the exposed portion of said coil, the web portion of said base member being spaced from said annular portions and said exposed portion of said coil, and leads for making external electrical connections to said device extending through said space between said base member web portion and at least one of said annular portions and attached to said coil at said exposed portion thereof.

8. A coaxial inductive device comprising a substantially cylindrical center winding leg member formed of magnetic material, annular portions formed of a plurality of relatively thin radially split washer-shaped laminations of magnetic material arranged on said center member respectively adjacent the ends thereof, a coil positioned on said center member intermediate said annular portions, a yoke member engaging the peripheral surface of said annular portions, said yoke member being formed of a plurality of relatively thin, flat, straight, radially arranged laminations of magnetic material and having a cross-section of less than a complete circle and more than a half circle thereby exposing a portion of said coil, a cover member having a cross-section of less than a complete circle and more than a half circle surrounding the peripheral surface of said yoke member and having inwardly turned portions formed on its circumferential ends respectively engaging the circumferential ends of said yoke member thereby holding said laminations in assembled relation, said cover member having inwardly turned annular flanges formed at its axial ends respectively engaging the axial ends of said yoke member, said circumferential ends of said cover member having outwardly turned portions formed thereon, a base member having a channel-shaped cross-section with the legs thereof inwardly inclined and engaging said cover member outwardly turned portions thereby enclosing the exposed portion of said coil, the web portion, of said base member being spaced from said annular portions and said exposed portion of said coil, and leads for making external electrical connections to said device extending through said space between said base member web portion and at least one of said annular portions and attached to said coil at said exposed portion thereof, said base member having portions extending respectively beyond the axial ends of said yoke member, said base member extension portions having their legs crimped thereby to hold said device in assembled relation and having mounting means formed thereon.

9. An enclosing case for a coaxial inductive device comprising a cover member having a cross-section of less than a complete circle and more than a half circle with outwardly and inwardly turned portions respectively formed on the circumferential ends thereof and inwardly turned annular flanges respectively formed on the axial ends thereof, and a base member having a channel-shaped cross-section with the legs thereof inwardly inclined and engaging said cover member outwardly turned portions.

References Cited in the file of this patent UNITED STATES PATENTS 518,805 Cooper Apr. 24, 1894 1,052,226 Douglas Feb. 4, 1913 2,324,181 Tulien July 13, 1943 2,508,241 Ferris May 16, 1950 2,531,697 Meyerhans Nov. 28, 1950 2,579,308 Dole Dec. 18, 1951 2,808,576 Brown Oct. 1, 1957 

